Hi I have a yanmar 3hm 35f engine and want to know the correct procedure for cleaning the foam air intake filter. The manual says clean every 250 hrs with a neutral detergent. Does that mean wash with detergent and water?

Yes, and does it also say re-oil with engineoil?
My Yanmar does not have the foam element, but oiling the foam to trap dirt is common, I'm going off of other engines experience here, do not know Yanmars recommendation. Many people clean foam elements in gasoline as it cleans the oil out really well and evaporates and mixes well with the oil when you re-oil the filter. If the filter is oiled and you clean it with soap and water, make sure it's very dry before re-oiling. Use a paper towel to absorb all the water it can and let it dry overnight.
I'm not recommending to go against the manufacturers recommendation with the gas comment, just explaining why you may hear to use gas.

BTW, an oiled foam air filter does a very good job of trapping dirt, used to be the standard for engines used in dirty environments like lawnmowers and dirt bikes.

Yes, and does it also say re-oil with engine oil?
My Yanmar does not have the foam element, but oiling the foam to trap dirt is common, I'm going off of other engines experience here, do not know Yanmars recommendation. Many people clean foam elements in gasoline as it cleans the oil out really well and evaporates and mixes well with the oil when you re-oil the filter. If the filter is oiled and you clean it with soap and water, make sure it's very dry before re-oiling. Use a paper towel to absorb all the water it can and let it dry overnight.
I'm not recommending to go against the manufacturers recommendation with the gas comment, just explaining why you may hear to use gas.

BTW, an oiled foam air filter does a very good job of trapping dirt, used to be the standard for engines used in dirty environments like lawnmowers and dirt bikes.

+1

Just depends on what ya got handy... I prefer to clean most anything with diesel... Dish soap and a sink/bucket will do a great job with the foam filter too...

__________________In the harsh marine environment, something is always in need of repair...

I have Yanmar 3GMF's in our cat and the recommended cleaning agant is white spirit and proper dtying afterwards. The filters for a marine engine should not be oiled, very little dust in the engine compartment compared to cars, and engines on the (dry/and dusty)land.

I believe any agent that cleans dirt and griume would do if the filters are of the foam type, however be careful to not use any strong soluble as this might disolve the foam.

I would have to agree with the "no oil" group with regard to the Yanmar filter.

I don't have information for the Yanmar 3hm 35f but my Yanmar 2GM20 is a dry foam filter.

__________________All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence

May depend on the engine type, foam type filters are generally Not oiled.
Clean with hot soapy water, dry throughly.
Check your service manual, you do have one, right?

Sent from my iPad SV Cloud Duster

Yes, depends on the filter.

I got tired of my junk Volvo foam filters dry rotting in a couple of sessons and replaced them with K&N filters (automotive industry). These have a cleaning solution and an oiling solution and an indefinately long life span. I've been running them for years.